1. Field
The present disclosure relates generally to electronics, and more specifically to transmitters and receivers.
2. Background
In a radio frequency (RF) transceiver, a communication signal is typically received and downconverted by receive circuitry, sometimes referred to as a receive chain. A receive chain typically includes a receive filter, a low noise amplifier (LNA), a mixer, a local oscillator (LO), a voltage controlled oscillator (VCO), a baseband filter, and other components, to recover the information contained in the communication signal. The transceiver also includes circuitry that enables the transmission of a communication signal to a receiver in another transceiver. The transceiver may be able to operate over multiple frequency ranges, typically referred to a frequency bands. Moreover, a single transceiver may be configured to operate using multiple carrier signals that may occur in the same frequency band, but that may not overlap in actual frequency, an arrangement referred to as non-contiguous carriers.
In some instances, it is desirable to have a single transmitter or receiver that is configured to operate using multiple transmit frequencies and/or multiple receive frequencies. For a receiver to be able to simultaneously receive two or more receive signals, the concurrent operation of two or more receive paths is generally required. Such systems are sometimes referred to as “carrier-aggregation” systems. The term “carrier-aggregation” may refer to systems that include inter-band carrier aggregation and intra-band carrier aggregation. Intra-band carrier aggregation refers to the processing of two separate carrier signals that occur in the same communication band. Inter-band carrier aggregation refers to the processing of two separate carrier signals that occur in different communication bands.
A prior receiver architecture uses multiple LNAs to support the simultaneous downlink channels. This architecture shorts the LNA inputs together to reduce the number of radio frequency (RF) connections used to interface with a transceiver. These prior LNAs can operate both stand-alone and simultaneously. Stand-alone operation refers to operating on a single carrier signal at a time; and simultaneous operation refers to operating on two or more carrier signals simultaneously. The outputs of these LNAs are separated to provide isolation between the different downlink channels. Usually these LNAs exhibit a degraded noise figure (NF) when simultaneously operating on multiple carriers as compared to when operating independently on a single carrier due to degradation of input matching and/or noise coupling between different signal paths when simultaneously operating on multiple carriers. In an effort to reduce circuit architecture size and reduce the number of ground connections, ground routings from the inductances of the LNAs to ground pins on the circuit become long, thus reducing LNA performance due to increased inductive coupling between different RF ground paths.
It would be desirable to reduce inductive coupling between different RF ground paths and improve receiver noise figure performance for a low nose amplifier architecture.